A method and device for modeling acoustic scattering of underwater targets based on linear time-varying system

Abstract

The present application provides a method and device for modeling acoustic scattering of underwater targets based on a linear time-varying system, the method comprising: segmenting and windowing an incident signal to obtain multiple sub-signal segments, wherein the similarity between the superposition results of the multiple sub-signal segments and the incident signal is greater than a preset threshold, and under the premise of meeting the distance resolution requirements and the frequency resolution requirements, during the duration of each sub-signal segment, the instantaneous radial velocity of each part of the target relative to the sonar position is considered unchanged; for each sub-signal segment, determining the acoustic scattering echo of the target as a whole for the current sub-signal segment; and obtaining the acoustic scattering echo of the target as a whole for the incident signal based on the superposition of the acoustic scattering echoes of the target as a whole for all sub-signal segments. Through the present application, the scattering process of the target to the incident signal is split from a linear time-varying system into a superposition state of multiple linear time-invariant systems, thereby effectively simulating the perturbation law of the target motion / micro-motion on the scattered sound field.

Description

Technical Field

[0001] The present application relates to the field of target detection technology, and in particular to a method and device for modeling underwater target acoustic scattering based on a linear time-varying system. Background Art

[0002] Active acoustic detection, as an important means of ocean detection technology, has been widely studied in theory and experiment. Scattering characteristics are the information source of active acoustic detection. Therefore, the study of acoustic scattering characteristics of underwater targets has always been a classic topic of ocean detection, and acoustic scattering modeling of underwater targets is its theoretical basis.

[0003] Underwater targets are divided into rigid targets such as submarines, UUVs (unmanned underwater vehicles) and torpedoes, and non-rigid targets such as frogmen, bionic UUVs and aquatic organisms. Non-rigid targets move forward by swinging themselves. When active sonar detects them, they not only have Doppler characteristics, but also have rich micro-Doppler characteristics due to the relative movement speed of various parts of the body during the swinging process. Similarly, rigid targets are mainly propelled by propellers. Although they only have Doppler characteristics when moving in a uniform straight line, they also have micro-Doppler characteristics when turning because of the different movement speeds of different parts relative to the sonar.

[0004] For underwater target acoustic scattering modeling, the prior art usually models acoustic scattering based on a linear time-invariant system, treating the scattering process as static and ignoring the modulation of a single pulse by the target motion / micromotion process. Therefore, it is only applicable to short pulse incidence or active detection of stationary targets. When the incident signal is long or the target moves quickly, and the target's posture movement during the duration of the incident signal cannot be ignored, the prior art cannot effectively simulate the disturbance law of the target motion / micromotion on the scattered acoustic field. Summary of the invention

[0005] The present application provides a method and device for modeling underwater target acoustic scattering based on a linear time-varying system, which can solve the technical problem in the prior art that when the posture movement of the target during the duration of the incident signal cannot be ignored, the disturbance law of the target movement / micro-motion on the scattered sound field cannot be effectively simulated.

[0006] In a first aspect, an embodiment of the present application provides a method for modeling acoustic scattering of underwater targets based on a linear time-varying system, and the method for modeling acoustic scattering of underwater targets includes:

[0007] The incident signal is segmented and windowed to obtain multiple sub-signal segments, wherein the similarity between the superposition result of the multiple sub-signal segments and the incident signal is greater than a preset threshold, and under the premise of meeting the requirements of range resolution and frequency resolution, during the duration of each sub-signal segment, the instantaneous radial velocity of each part of the target relative to the sonar position is considered unchanged;

[0008] For each sub-signal segment, determining the acoustic scattering echo of the target as a whole for the current sub-signal segment;

[0009] The acoustic scattering echo of the entire target for the incident signal is obtained by superimposing the acoustic scattering echo of the entire target for all sub-signal segments.

[0010] Furthermore, in one embodiment, the step of segmentally windowing the incident signal to obtain a plurality of sub-signal segments includes:

[0011] Perform zero padding on the front section of the incident signal, and perform windowing on the incident signal after the zero padding in the front section to obtain multiple sub-signal segments;

[0012] The step of obtaining the acoustic scattering echo of the entire target for the incident signal by superimposing the acoustic scattering echo of the entire target for all sub-signal segments comprises:

[0013] The acoustic scattering echoes of the entire target for all sub-signal segments are superimposed to obtain an intermediate result, and the intermediate result is pre-zeroed to obtain the acoustic scattering echo of the entire target for the incident signal, wherein the zero removal length is equal to the zero filling length.

[0014] Furthermore, in one embodiment, the calculation formula of the zero padding length is:

[0015] zeroLen = N*(WndLen – overlapLen)+overlapLen;

[0016] Among them, zeroLen is the zero-padding length, WndLen is the time window length of the segmented windowing, overlapLen is the length of the overlapping part of the segmented windowing, and N is a positive integer.

[0017] Furthermore, in one embodiment, the step of determining the acoustic scattering echo of the entire target for the current sub-signal segment includes:

[0018] For each part of the target: let the sonar be in a stationary system and the current part be in a moving system; according to the sound speed in water and the instantaneous radial velocity of the current part relative to the sonar position during the duration of the current sub-signal segment, perform Lorentz transformation on the current sub-signal segment in the stationary system to obtain the current sub-signal segment in the moving system; calculate the acoustic scattering impact response function of the current part by the plate element method; convolve the current sub-signal segment in the moving system with the acoustic scattering impact response function of the current part to obtain the acoustic scattering echo of the current part for the current sub-signal segment in the moving system; according to the sound speed in water and the instantaneous radial velocity of the current part relative to the sonar position during the duration of the current sub-signal segment, perform Lorentz transformation on the acoustic scattering echo of the current part for the current sub-signal segment in the moving system to obtain the acoustic scattering echo of the current part for the current sub-signal segment in the stationary system;

[0019] The acoustic scattering echo of the entire target for the current sub-signal segment in the stationary system is obtained by superimposing the acoustic scattering echo of all parts of the target for the current sub-signal segment in the stationary system.

[0020] Furthermore, in one embodiment, before the step of calculating the acoustic scattering impact response function of the current part by the plate element method, the step further includes:

[0021] The frequency range of the acoustic scattering impact response function to be solved at the current position is determined according to the frequency range of the current sub-signal segment under the motion system.

[0022] Furthermore, in one embodiment, in the Lorentz transformation, the relationship between the moving frame time and the stationary frame time is:

[0023]

[0024] Among them, t is the stationary time, t' is the moving time, c is the speed of sound in water, and v is the instantaneous radial velocity of the current position relative to the sonar position during the duration of the current sub-signal segment.

[0025] Furthermore, in one embodiment, after the step of segmenting and windowing the incident signal to obtain a plurality of sub-signal segments, the step further includes:

[0026] A moving target model is established according to the shape information of the target and the movement information of the target during the duration of the incident signal, and the coordinate information of the sonar is determined in the coordinate system of the moving target model;

[0027] Performing grid division and grid coordinate extraction on the moving target model to obtain the coordinate information of each grid at the start time and the end time of each sub-signal segment, wherein each grid corresponds to a part of the target;

[0028] According to the sub-signal segment length, the sonar coordinate information and the coordinate information of each grid at the start and end time of each sub-signal segment, the instantaneous radial velocity of each part of the target relative to the sonar position during the duration of each sub-signal segment is calculated.

[0029] In a second aspect, an embodiment of the present application further provides an underwater target acoustic scattering modeling device based on a linear time-varying system, the underwater target acoustic scattering modeling device comprising:

[0030] A segmented windowing module is used to segmentally window the incident signal to obtain multiple sub-signal segments, wherein the similarity between the superposition result of the multiple sub-signal segments and the incident signal is greater than a preset threshold, and under the premise of meeting the requirements of range resolution and frequency resolution, during the duration of each sub-signal segment, the instantaneous radial velocity of each part of the target relative to the sonar position is considered unchanged;

[0031] An echo analysis module, for determining, for each sub-signal segment, the acoustic scattering echo of the target as a whole for the current sub-signal segment;

[0032] The echo superposition module is used to obtain the acoustic scattering echo of the entire target for the incident signal by superimposing the acoustic scattering echo of the entire target for all sub-signal segments.

[0033] Further, in one embodiment, the segmented windowing module is used to:

[0034] Perform zero padding on the front section of the incident signal, and perform windowing on the incident signal after the zero padding in the front section to obtain multiple sub-signal segments;

[0035] The echo stacking module is used to:

[0036] The acoustic scattering echoes of the entire target for all sub-signal segments are superimposed to obtain an intermediate result, and the intermediate result is pre-zeroed to obtain the acoustic scattering echo of the entire target for the incident signal, wherein the zero removal length is equal to the zero filling length.

[0037] Furthermore, in one embodiment, the calculation formula of the zero padding length is:

[0038] zeroLen = N*(WndLen – overlapLen)+overlapLen;

[0039] Among them, zeroLen is the zero-padding length, WndLen is the time window length of the segmented windowing, overlapLen is the length of the overlapping part of the segmented windowing, and N is a positive integer.

[0040] In the present application, when the incident signal is long or the target moves quickly, and the target's posture movement during the duration of the incident signal cannot be ignored, the target's scattering process of the incident signal is a linear time-varying system. The incident signal is converted into multiple sub-signal segments through a segmented windowing operation, so that the target's scattering process for each sub-signal segment is a linear time-invariant system. Based on the linear time-invariant system, the acoustic scattering echo of the target as a whole for each sub-signal segment is determined separately, and finally the acoustic scattering echo of the target as a whole for the incident signal is obtained by summarizing and superimposing. Through the present application, the scattering process of the target for the incident signal is split from a linear time-varying system into a superposition state of multiple linear time-invariant systems, thereby effectively simulating the perturbation law of the scattered sound field caused by the target movement / micro-motion. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 It is a flow chart of a method for modeling acoustic scattering of underwater targets based on a linear time-varying system in one embodiment of the present application;

[0042] Figure 2 A schematic diagram of signal processing in a method for modeling acoustic scattering of underwater targets in one embodiment of the present application;

[0043] Figure 3 A schematic diagram of a Lorentz transformation in an embodiment of the present application;

[0044] Figure 4 Schematic diagram of the functional modules of an underwater target acoustic scattering modeling device based on a linear time-varying system in one embodiment of the present application. DETAILED DESCRIPTION

[0045] In order to enable those skilled in the art to better understand the solution of the present application, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0046] In order to make the objectives, technical solutions and advantages of the present application clearer, the implementation methods of the present application will be further described in detail below with reference to the accompanying drawings.

[0047] In a first aspect, an embodiment of the present application provides a method for modeling acoustic scattering of underwater targets based on a linear time-varying system.

[0048] Figure 1 A flow chart of a method for modeling acoustic scattering of underwater targets based on a linear time-varying system in an embodiment of the present application is shown.

[0049] Reference Figure 1 In one embodiment, the method for modeling acoustic scattering of underwater targets includes the following steps:

[0050] S11. Segment and window the incident signal to obtain multiple sub-signal segments, wherein the similarity between the superposition result of the multiple sub-signal segments and the incident signal is greater than a preset threshold, and under the premise of meeting the distance resolution requirement and the frequency resolution requirement, during the duration of each sub-signal segment, the instantaneous radial velocity of each part of the target relative to the sonar position is considered unchanged.

[0051] Specifically, when the incident signal is long or the target moves quickly, and the target's posture movement during the duration of the incident signal cannot be ignored, the target's scattering process of the incident signal is a linear time-varying system. Therefore, the acoustic scattering modeling method based on the linear time-invariant system in the prior art is not applicable to this situation.

[0052] In this embodiment, there are two basic requirements for the segmented windowing operation. The first is that the similarity between the superposition result of multiple sub-signal segments and the incident signal is greater than a preset threshold, that is, the superposition result of multiple sub-signal segments is basically consistent with the incident signal, thereby minimizing the error introduced by the signal input link. The second is that under the premise of meeting the distance resolution requirements and the frequency resolution requirements, during the duration of each sub-signal segment, the instantaneous radial velocity of each part of the target relative to the sonar position is regarded as unchanged, that is, the scattering process of the target for each sub-signal segment is regarded as a linear time-invariant system, thereby ensuring the accuracy of acoustic scattering modeling for sub-signal segments based on the linear time-invariant system.

[0053] Specifically, distance resolution is the ability to detect targets that are very close to each other as different targets, and frequency resolution is the ability to separate two adjacent spectral peaks and distinguish different frequency components. To meet the requirements of these two dimensions, after selecting the window function, first determine the optional range of the time window length and the length of the overlapping part based on the pre-defined target motion conditions, then combine the superposition result with the similarity requirements of the incident signal, and finally determine the time window length and the length of the overlapping part. According to the window function, the time window length and the length of the overlapping part, the incident signal is segmented and windowed.

[0054] Specifically, the instantaneous radial velocity of a certain part of the target relative to the sonar position refers to the component of the instantaneous velocity of the part relative to the sonar position in the direction from the sonar position to the part.

[0055] By way of example, the incident signal is a pulse of a long pulse signal or a continuous wave signal.

[0056] Optionally, the window function is a Hanning window or a Hamming window.

[0057] S12. For each sub-signal segment, determine the acoustic scattering echo of the entire target for the current sub-signal segment.

[0058] In this embodiment, during the duration of different sub-signal segments, the azimuth of the same part of the target relative to the sonar position may change, resulting in a change in the acoustic scattering impulse response function, and the instantaneous radial velocity may also change, resulting in a change in the Doppler frequency shift. The scattering process of the target for each sub-signal segment is regarded as a linear time-invariant system under different characteristic parameters, and the acoustic scattering echo of the target as a whole for each sub-signal segment is determined separately, which can improve the accuracy of acoustic scattering modeling.

[0059] Optionally, the acoustic scattering modeling method used in step S12 may be a method in the prior art, or may be an improved method based on the prior art.

[0060] S13, obtaining the acoustic scattering echo of the entire target for the incident signal by superimposing the acoustic scattering echo of the entire target for all sub-signal segments.

[0061] Therefore, in this embodiment, when the incident signal is long or the target moves quickly, and the target's posture movement during the duration of the incident signal cannot be ignored, the target's scattering process of the incident signal is a linear time-varying system, and the incident signal is converted into multiple sub-signal segments through a segmented windowing operation, so that the target's scattering process for each sub-signal segment is a linear time-invariant system, and the acoustic scattering echo of the target as a whole for each sub-signal segment is determined based on the linear time-invariant system, and finally the acoustic scattering echo of the target as a whole for the incident signal is obtained by summarizing and superimposing. Through this embodiment, the scattering process of the target for the incident signal is split from a linear time-varying system into a superposition state of multiple linear time-invariant systems, thereby effectively simulating the perturbation law of the target motion / micro-motion on the scattered sound field.

[0062] Figure 2 A signal processing schematic diagram of a method for modeling acoustic scattering of underwater targets in one embodiment of the present application is shown.

[0063] Reference Figure 2 Further, in one embodiment, the step of segmenting and windowing the incident signal to obtain a plurality of sub-signal segments includes:

[0064] Perform zero padding on the front section of the incident signal, and perform windowing on the incident signal after the zero padding in the front section to obtain multiple sub-signal segments;

[0065] The step of obtaining the acoustic scattering echo of the entire target for the incident signal by superimposing the acoustic scattering echo of the entire target for all sub-signal segments comprises:

[0066] The acoustic scattering echoes of the entire target for all sub-signal segments are superimposed to obtain an intermediate result, and the intermediate result is pre-zeroed to obtain the acoustic scattering echo of the entire target for the incident signal, wherein the zero removal length is equal to the zero filling length.

[0067] In this embodiment, zero padding is performed before the incident signal is segmented and windowed, thereby further reducing the information loss caused by the segmented windowing. Since the length of the incident signal is redundant, only the front segment needs to be zero-padding, and the back segment does not need to be zero-padding.

[0068] It should be noted that Figure 2 The convolution in specifically refers to convolving each sub-signal segment with the acoustic scattering impulse response function of each part of the target in the time domain to determine the acoustic scattering echo of each part of the target for each sub-signal segment. h(m,n) refers to the acoustic scattering impulse response function of the m-th part of the target during the duration of the n-th sub-signal segment. This is an optional implementation method of acoustic scattering modeling and does not represent a limitation on this embodiment. Other methods can also be used for acoustic scattering modeling in this embodiment.

[0069] Furthermore, in one embodiment, the calculation formula of the zero padding length is:

[0070] zeroLen = N*(WndLen – overlapLen)+overlapLen;

[0071] Among them, zeroLen is the zero-padding length, WndLen is the time window length of the segmented windowing, overlapLen is the length of the overlapping part of the segmented windowing, and N is a positive integer.

[0072] Through this embodiment, the zero-padding length is reasonably set, which helps to optimize the frequency resolution and reduce spectrum leakage.

[0073] Furthermore, in one embodiment, the step of determining the acoustic scattering echo of the entire target for the current sub-signal segment includes:

[0074] For each part of the target: let the sonar be in a stationary system and the current part be in a moving system; according to the sound speed in water and the instantaneous radial velocity of the current part relative to the sonar position during the duration of the current sub-signal segment, perform Lorentz transformation on the current sub-signal segment in the stationary system to obtain the current sub-signal segment in the moving system; calculate the acoustic scattering impact response function of the current part by the plate element method; convolve the current sub-signal segment in the moving system with the acoustic scattering impact response function of the current part to obtain the acoustic scattering echo of the current part for the current sub-signal segment in the moving system; according to the sound speed in water and the instantaneous radial velocity of the current part relative to the sonar position during the duration of the current sub-signal segment, perform Lorentz transformation on the acoustic scattering echo of the current part for the current sub-signal segment in the moving system to obtain the acoustic scattering echo of the current part for the current sub-signal segment in the stationary system;

[0075] The acoustic scattering echo of the entire target for the current sub-signal segment in the stationary system is obtained by superimposing the acoustic scattering echo of all parts of the target for the current sub-signal segment in the stationary system.

[0076] In this embodiment, since the speed of the target moving in the water is much slower than the speed of sound, the change in the amplitude of the scattered echo caused by the Doppler effect can be ignored. The moving point sound source is solved by the Lorentz transformation to achieve the solution of the Doppler frequency shift. Compared with using the Doppler calculation formula to solve the offset of each frequency point in the frequency domain, the calculation can be simplified.

[0077] It is specially noted that the sub-signal segments and acoustic scattering echoes without a specified coordinate system in this article all refer to the sub-signal segments and acoustic scattering echoes in the stationary system, and the signals in the stationary system and the signals in the moving system are converted into each other through the Lorentz transformation.

[0078] Figure 3 A schematic diagram of the Lorentz transformation in an embodiment of the present application is shown.

[0079] Reference Figure 3, each part of the target has a separate instantaneous radial velocity, and the motion system corresponds to the target part one by one. Figure 3 Taking two parts of the target as an example, the current sub-signal segment in the stationary system is represented as y(t), and the i-th part of the target corresponds to the moving system i, and the current sub-signal segment in the moving system i is represented as y (i) (t (i) ), the jth part of the target corresponds to motion system j, and the current sub-signal segment under motion system j is represented by y (j) (t (j) ).

[0080] Optionally, the plate element method may use numerical methods such as the finite element method or the Kirchhoff approximation. When calculating the plate element method, at least the frequency range to be solved and the orientation of the corresponding part of the target relative to the sonar position need to be specified.

[0081] Furthermore, in one embodiment, before the step of calculating the acoustic scattering impact response function of the current part by the plate element method, the step further includes:

[0082] The frequency range of the acoustic scattering impact response function to be solved at the current position is determined according to the frequency range of the current sub-signal segment under the motion system.

[0083] In this embodiment, with the help of the frequency range of the current sub-signal segment in the motion system, the frequency range of the acoustic scattering impact response function of the current part to be solved can be reasonably determined, thereby reducing the amount of calculation.

[0084] It can be understood that in this embodiment, since the frequency range of the acoustic scattering impact response function to be solved needs to be determined with the help of the frequency range of the current sub-signal segment in the motion system, the Lorentz transformation of the sub-signal segment needs to be performed before the calculation of the acoustic scattering impact response function, and the current sub-signal segment in the motion system needs to be analyzed in the frequency domain to determine its frequency range.

[0085] In other embodiments, a wider frequency range may be selected based on experience, so that the calculation of the acoustic scattering impulse response function may be performed before or synchronously with the Lorentz transformation of the sub-signal segment.

[0086] For example, in the Lorentz transformation, the relationship between the moving frame time and the stationary frame time is:

[0087]

[0088] Among them, t is the stationary time, t' is the moving time, c is the speed of sound in water, and v is the instantaneous radial velocity of the current position relative to the sonar position during the duration of the current sub-signal segment.

[0089] Furthermore, in one embodiment, after the step of segmenting and windowing the incident signal to obtain a plurality of sub-signal segments, the step further includes:

[0090] A moving target model is established according to the shape information of the target and the movement information of the target during the duration of the incident signal, and the coordinate information of the sonar is determined in the coordinate system of the moving target model;

[0091] Performing grid division and grid coordinate extraction on the moving target model to obtain the coordinate information of each grid at the start time and the end time of each sub-signal segment, wherein each grid corresponds to a part of the target;

[0092] According to the sub-signal segment length, the sonar coordinate information and the coordinate information of each grid at the start and end time of each sub-signal segment, the instantaneous radial velocity of each part of the target relative to the sonar position during the duration of each sub-signal segment is calculated.

[0093] Specifically, the shape information of the target and the motion information of the target during the duration of the incident signal are pre-defined information. The moving target model is used to simulate the overall motion characteristics of the target and the local micro-motion characteristics of the target during the duration of the incident signal. By gridding the moving target model and extracting grid coordinates, each grid corresponds to a part of the target, and the coordinate information of each part of the target at each sampling moment can be obtained. Since the instantaneous radial velocity of each part of the target relative to the sonar position is considered unchanged during the duration of each sub-signal segment, the calculation of the instantaneous radial velocity only requires the coordinate information of the start and end times of each sub-signal segment.

[0094] For example, the sampling moments include t0, t2, t3, ..., t 100 , the time interval between adjacent moments is Δt, and the sub-signal segment includes t0-t 20 ,t 10 -t 30 ,t 20 -t 40 ,……,t 80 -t 100 , for t0-t 20 The sub-signal segment is based on the sub-signal segment length 20Δt, the sonar coordinate information and each grid at t0 and t 20 The coordinate information of each part of the target is calculated at t0-t 20 The instantaneous radial velocity relative to the sonar position during the duration of the sub-segment, and so on.

[0095] For example, the grid size may be set with reference to the wavelength corresponding to the upper frequency limit of the incident signal.

[0096] In a second aspect, an embodiment of the present application further provides an underwater target acoustic scattering modeling device based on a linear time-varying system.

[0097] Figure 4 A schematic diagram of functional modules of an underwater target acoustic scattering modeling device based on a linear time-varying system in an embodiment of the present application is shown.

[0098] Reference Figure 4 In one embodiment, the underwater target acoustic scattering modeling device includes:

[0099] The segmented windowing module 10 is used to segmentally window the incident signal to obtain a plurality of sub-signal segments, wherein the similarity between the superposition result of the plurality of sub-signal segments and the incident signal is greater than a preset threshold, and under the premise of meeting the requirements of range resolution and frequency resolution, during the duration of each sub-signal segment, the instantaneous radial velocity of each part of the target relative to the sonar position is regarded as unchanged;

[0100] The echo analysis module 20 is used to determine the acoustic scattering echo of the target as a whole for the current sub-signal segment for each sub-signal segment;

[0101] The echo superposition module 30 is used to obtain the acoustic scattering echo of the entire target for the incident signal by superimposing the acoustic scattering echo of the entire target for all sub-signal segments.

[0102] Furthermore, in one embodiment, the segmented windowing module 10 is used to:

[0103] Perform zero padding on the front section of the incident signal, and perform windowing on the incident signal after the zero padding in the front section to obtain multiple sub-signal segments;

[0104] The echo superposition module 30 is used for:

[0105] The acoustic scattering echoes of the entire target for all sub-signal segments are superimposed to obtain an intermediate result, and the intermediate result is pre-zeroed to obtain the acoustic scattering echo of the entire target for the incident signal, wherein the zero removal length is equal to the zero filling length.

[0106] Furthermore, in one embodiment, the calculation formula of the zero padding length is:

[0107] zeroLen = N*(WndLen – overlapLen)+overlapLen;

[0108] Among them, zeroLen is the zero-padding length, WndLen is the time window length of the segmented windowing, overlapLen is the length of the overlapping part of the segmented windowing, and N is a positive integer.

[0109] Furthermore, in one embodiment, the echo analysis module 20 is used to:

[0110] For each part of the target: let the sonar be in a stationary system and the current part be in a moving system; according to the sound speed in water and the instantaneous radial velocity of the current part relative to the sonar position during the duration of the current sub-signal segment, perform Lorentz transformation on the current sub-signal segment in the stationary system to obtain the current sub-signal segment in the moving system; calculate the acoustic scattering impact response function of the current part by the plate element method; convolve the current sub-signal segment in the moving system with the acoustic scattering impact response function of the current part to obtain the acoustic scattering echo of the current part for the current sub-signal segment in the moving system; according to the sound speed in water and the instantaneous radial velocity of the current part relative to the sonar position during the duration of the current sub-signal segment, perform Lorentz transformation on the acoustic scattering echo of the current part for the current sub-signal segment in the moving system to obtain the acoustic scattering echo of the current part for the current sub-signal segment in the stationary system;

[0111] The acoustic scattering echo of the entire target for the current sub-signal segment in the stationary system is obtained by superimposing the acoustic scattering echo of all parts of the target for the current sub-signal segment in the stationary system.

[0112] Furthermore, in one embodiment, the echo analysis module 20 is also used for:

[0113] The frequency range of the acoustic scattering impact response function to be solved at the current position is determined according to the frequency range of the current sub-signal segment under the motion system.

[0114] Furthermore, in one embodiment, in the Lorentz transformation, the relationship between the moving frame time and the stationary frame time is:

[0115]

[0116] Among them, t is the stationary time, t' is the moving time, c is the speed of sound in water, and v is the instantaneous radial velocity of the current position relative to the sonar position during the duration of the current sub-signal segment.

[0117] Furthermore, in one embodiment, the underwater target acoustic scattering modeling device further includes a velocity calculation module for:

[0118] A moving target model is established according to the shape information of the target and the movement information of the target during the duration of the incident signal, and the coordinate information of the sonar is determined in the coordinate system of the moving target model;

[0119] Performing grid division and grid coordinate extraction on the moving target model to obtain the coordinate information of each grid at the start time and the end time of each sub-signal segment, wherein each grid corresponds to a part of the target;

[0120] According to the sub-signal segment length, the sonar coordinate information and the coordinate information of each grid at the start and end time of each sub-signal segment, the instantaneous radial velocity of each part of the target relative to the sonar position during the duration of each sub-signal segment is calculated.

[0121] Among them, the functional implementation of each module in the above-mentioned underwater target acoustic scattering modeling device corresponds to each step in the above-mentioned underwater target acoustic scattering modeling method embodiment, and its functions and implementation processes are no longer repeated here.

[0122] It should be noted that the serial numbers of the above-mentioned embodiments of the present application are only for description and do not represent the advantages or disadvantages of the embodiments.

[0123] The terms "including" and "having" and any variations thereof in the specification and claims of this application and the above-mentioned drawings are intended to cover non-exclusive inclusions. For example, a process, method, system, product or device that includes a series of steps or units is not limited to the listed steps or units, but optionally includes steps or units that are not listed, or optionally includes other steps or units inherent to these processes, methods, products or devices. The terms "first", "second" and "third" are used to distinguish different objects, etc., and do not represent a sequence, nor do they limit "first", "second" and "third" to different types.

[0124] In the description of the embodiments of the present application, "exemplary", "for example" or "for example" are used to indicate examples, illustrations or descriptions. Any embodiment or design described as "exemplary", "for example" or "for example" in the embodiments of the present application should not be interpreted as being more preferred or more advantageous than other embodiments or designs. Specifically, the use of words such as "exemplary", "for example" or "for example" is intended to present related concepts in a specific way.

[0125] In the description of the embodiments of the present application, unless otherwise specified, “ / ” means or. For example, A / B can mean A or B. The “and / or” in the text is merely a description of the association relationship of associated objects, indicating that three relationships may exist. For example, A and / or B can mean: A exists alone, A and B exist at the same time, and B exists alone. In addition, in the description of the embodiments of the present application, “multiple” refers to two or more than two.

[0126] In some processes described in the embodiments of the present application, multiple operations or steps that appear in a specific order are included, but it should be understood that these operations or steps may not be executed in the order in which they appear in the embodiments of the present application or in parallel, and the sequence number of the operation is only used to distinguish the different operations, and the sequence number itself does not represent any execution order. In addition, these processes may include more or fewer operations, and these operations or steps may be executed in sequence or in parallel, and these operations or steps may be combined.

[0127] Through the description of the above implementation methods, those skilled in the art can clearly understand that the above-mentioned embodiment methods can be implemented by means of software plus a necessary general hardware platform, and of course by hardware, but in many cases the former is a better implementation method. Based on such an understanding, the technical solution of the present application is essentially or the part that contributes to the prior art can be embodied in the form of a software product, which is stored in a storage medium (such as ROM / RAM, disk, CD) as described above, and includes a number of instructions for a terminal device to execute the methods described in each embodiment of the present application.

[0128] The above are only preferred embodiments of the present application, and are not intended to limit the patent scope of the present application. Any equivalent structure or equivalent process transformation made using the contents of the present application specification and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present application.

Claims

1. A method for modeling underwater target acoustic scattering based on a linear time-varying system, characterized in that: The underwater target acoustic scattering modeling method comprises: The incident signal is segmented and windowed to obtain multiple sub-signal segments, wherein the similarity between the superposition result of the multiple sub-signal segments and the incident signal is greater than a preset threshold, and under the premise of meeting the requirements of range resolution and frequency resolution, during the duration of each sub-signal segment, the instantaneous radial velocity of each part of the target relative to the sonar position is considered unchanged; For each sub-signal segment, determining the acoustic scattering echo of the target as a whole for the current sub-signal segment; The acoustic scattering echo of the entire target for the incident signal is obtained by superimposing the acoustic scattering echo of the entire target for all sub-signal segments.

2. The underwater target acoustic scattering modeling method according to claim 1, characterized in that: The step of segmenting and windowing the incident signal to obtain a plurality of sub-signal segments comprises: Perform zero padding on the front section of the incident signal, and perform windowing on the incident signal after the zero padding in the front section to obtain multiple sub-signal segments; The step of obtaining the acoustic scattering echo of the entire target for the incident signal by superimposing the acoustic scattering echo of the entire target for all sub-signal segments comprises: The acoustic scattering echoes of the entire target for all sub-signal segments are superimposed to obtain an intermediate result, and the intermediate result is pre-zeroed to obtain the acoustic scattering echo of the entire target for the incident signal, wherein the zero removal length is equal to the zero filling length.

3. The underwater target acoustic scattering modeling method according to claim 2, characterized in that: The formula for calculating the zero-padding length is: zeroLen = N*(WndLen – overlapLen)+overlapLen; Among them, zeroLen is the zero-padding length, WndLen is the time window length of the segmented windowing, overlapLen is the length of the overlapping part of the segmented windowing, and N is a positive integer.

4. The underwater target acoustic scattering modeling method according to claim 1, characterized in that: The step of determining the acoustic scattering echo of the entire target for the current sub-signal segment comprises: For each part of the target: let the sonar be in a stationary system and the current part be in a moving system; according to the sound speed in water and the instantaneous radial velocity of the current part relative to the sonar position during the duration of the current sub-signal segment, perform Lorentz transformation on the current sub-signal segment in the stationary system to obtain the current sub-signal segment in the moving system; calculate the acoustic scattering impact response function of the current part by the plate element method; convolve the current sub-signal segment in the moving system with the acoustic scattering impact response function of the current part to obtain the acoustic scattering echo of the current part for the current sub-signal segment in the moving system; according to the sound speed in water and the instantaneous radial velocity of the current part relative to the sonar position during the duration of the current sub-signal segment, perform Lorentz transformation on the acoustic scattering echo of the current part for the current sub-signal segment in the moving system to obtain the acoustic scattering echo of the current part for the current sub-signal segment in the stationary system; The acoustic scattering echo of the entire target for the current sub-signal segment in the stationary system is obtained by superimposing the acoustic scattering echo of all parts of the target for the current sub-signal segment in the stationary system.

5. The underwater target acoustic scattering modeling method according to claim 4, characterized in that: Before the step of calculating the acoustic scattering impact response function of the current part by the plate element method, the method further includes: The frequency range of the acoustic scattering impact response function to be solved at the current position is determined according to the frequency range of the current sub-signal segment under the motion system.

6. The underwater target acoustic scattering modeling method according to claim 4, characterized in that: In the Lorentz transformation, the relationship between the moving frame time and the stationary frame time is: Among them, t is the stationary time, t' is the moving time, c is the speed of sound in water, and v is the instantaneous radial velocity of the current position relative to the sonar position during the duration of the current sub-signal segment.

7. The underwater target acoustic scattering modeling method according to claim 1, characterized in that: After the step of windowing the incident signal segment by segment to obtain a plurality of sub-signal segments, the method further includes: A moving target model is established according to the shape information of the target and the movement information of the target during the duration of the incident signal, and the coordinate information of the sonar is determined in the coordinate system of the moving target model; Performing grid division and grid coordinate extraction on the moving target model to obtain the coordinate information of each grid at the start time and the end time of each sub-signal segment, wherein each grid corresponds to a part of the target; According to the sub-signal segment length, the sonar coordinate information and the coordinate information of each grid at the start and end time of each sub-signal segment, the instantaneous radial velocity of each part of the target relative to the sonar position during the duration of each sub-signal segment is calculated.

8. A device for modeling underwater target acoustic scattering based on a linear time-varying system, characterized in that: The underwater target acoustic scattering modeling device comprises: A segmented windowing module is used to segmentally window the incident signal to obtain multiple sub-signal segments, wherein the similarity between the superposition result of the multiple sub-signal segments and the incident signal is greater than a preset threshold, and under the premise of meeting the requirements of range resolution and frequency resolution, during the duration of each sub-signal segment, the instantaneous radial velocity of each part of the target relative to the sonar position is considered unchanged; An echo analysis module, for determining, for each sub-signal segment, the acoustic scattering echo of the target as a whole for the current sub-signal segment; The echo superposition module is used to obtain the acoustic scattering echo of the entire target for the incident signal by superimposing the acoustic scattering echo of the entire target for all sub-signal segments.

9. The underwater target acoustic scattering modeling device according to claim 8, characterized in that: The segmented windowing module is used to: Perform zero padding on the front section of the incident signal, and perform windowing on the incident signal after the zero padding in the front section to obtain multiple sub-signal segments; The echo stacking module is used to: The acoustic scattering echoes of the entire target for all sub-signal segments are superimposed to obtain an intermediate result, and the intermediate result is pre-zeroed to obtain the acoustic scattering echo of the entire target for the incident signal, wherein the zero removal length is equal to the zero filling length.

10. The underwater target acoustic scattering modeling device according to claim 9, characterized in that: The formula for calculating the zero-padding length is: zeroLen = N*(WndLen – overlapLen)+overlapLen; Among them, zeroLen is the zero-padding length, WndLen is the time window length of the segmented windowing, overlapLen is the length of the overlapping part of the segmented windowing, and N is a positive integer.

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